1. Field of the Invention
This invention relates to a low pressure casting apparatus and more particularly to a casting apparatus having two independent manipulator arms mounted for independent motion with respect to a single low pressure furnace.
2. Description of the Prior Art
Low pressure casting of brass or bronze castings generally employ a low pressure furnace which is filled with molten metal, the molten metal being forced through an ascending pipe or pipes in the furnace into the mold or molds. The molds are mounted in various ways for step by step movement in sequence into engagement with the ascending pipe of the furnace. The molds are simultaneously moved to a discharge station where the casting is removed, a washing station for cleaning the mold surfaces and a core setting station for placing a core in the mold. In order to efficiently produce castings, one of the essential requirements is to present the molds to the furnace in a timed alternating sequence.
One system which achieves this function is disclosed and described in U.S. Pat. No. 4,431,046 entitled "Automated Low Pressure Casting Mechanism and Method" issued on Feb. 14, 1984. In this system, a number of mold manipulators are mounted on a revolving table or carousel which is rotated to sequentially position one of the molds on the casting furnace. The molds must be sequenced in steps in order to discharge, wash and set cores in the molds prior to being presented to the furnace. In this patent, the sequence of steps is controlled by the time required to fill the mold, which is the longest time required for any of the steps. If for any reason one of the mold manipulators becomes inoperable due to breakage of the mold or breakdown of the system, the entire system must be shut down until the manipulator is replaced or the mold is repaired or replaced. The productivity of the furnace is lost during such a shutdown period. Additional productivity of the system is lost due to the time required to bring the system back to ideal operating conditions.